The present invention relates to an engine unit for a small-sized motor vehicle (compact car).
Recently, however, a body, an engine and so on of a small-sized vehicle such as scooter-type motorcycle have been made large, and hence, it becomes difficult to attach or mount a swing-type engine unit, in which the engine and a power transmission unit is integrated together, to the motorcycle body to be swingable. This is because, in accordance with the requirement of the large size of the vehicle, the engine unit has a long size in its longitudinal direction and, hence, the entire length of the vehicle body is also made long. Moreover, according to such long structure, a gravity point of the vehicle is displaced to a rearward position and a load to be applied to front wheels is reduced, thus being made hard to design an alignment achieving steering and running stabilities.
To solve such inconvenience, in these days, there is provided a vehicle of the type in which an engine unit is fixed to a vehicle body and only its transmission unit is separated from the engine unit and mounted to the vehicle body to be swingable to thereby arrange the engine unit to a forward position of the vehicle body.
Further, in a general structure, a power generation portion and a speed changing portion are mounted or housed integrally in an inside of an engine unit case. However, in an arrangement in which the power generation portion and the speed changing portion are mounted or housed integrally in an inside of the engine unit case, the engine unit is made large and number of parts or elements is increased.
Moreover, a production line for manufacturing the engine unit is made long and assembling working thereof is not effectively performed on the production line.
Furthermore, the increasing of the number of the parts makes complicated quality check or inspection, and in a case where a defective is found out, it is difficult to disassemble or reassemble the parts. It is also necessary to prepare a new unit case in a case of different engine displacement or usage of engine unit, thus being inconvenient and being not economical. Still furthermore, in the arrangement in which the power generation portion and the speed changing portion are housed integrally in an inside of the engine unit case, there is a fear of transferring a heat generated at the power generation portion to the speed changing portion, thus being inconvenient.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art described above and to provide an engine unit of a small-sized vehicle such as scooter-type motorcycle achieving an improvement of the productivity thereof by integrally combining respective independent sections of the vehicle structure.
This and other objects can be achieved according to the present invention by providing an engine unit of a small-sized vehicle including an engine unit and a power transmission unit coupled to the engine unit to be swingable, the engine unit comprising:
a power generation section;
a speed changing section;
a first case into which the power generation unit is accommodated; and
a second case into which the speed changing section is accommodated,
wherein the first and second cases are operatively connected to each other as a unit case constituting the engine unit, which is then mounted to a vehicle body.
In a preferred embodiment, the first and second cases provide substantially L-shape in plan views respectively and are opposed to each other so that longitudinal portions of the L-shaped portions thereof are overlapped to each other in a width direction of the vehicle body.
The first and second cases are coupled together with a space therebetween. The second case is formed with an exhaust port so as to be opened to the space.
More in detail, the power generation section includes an engine body and the speed changing section includes a first speed changing section as a transmission section and a second speed changing section as a differential section which is connected to the transmission section. The first case is a crank case and the second case includes a transmission case and a differential case.
The crank case, the transmission case and the differential case are coupled together as an integral unit which is to be mounted to a vehicle body frame by means of blots.
According to the structures of the present invention mentioned above, in which the crank case, the transmission case and the differential case are coupled together into an engine unit, the following advantageous functions and effects can be achieved.
The respective portions or members of the vehicle can be made compact and the number thereof to be used can be reduced, so that the respective product assembling or manufacturing lines can be made short. Thus, the quality checking can be easily and effectively done for every sections, being convenient in its handling even if defective is caused.
Since the respective sections are separated from each other, many variation in design or structure can be selected optionally by changing only one or two of them, and as a result, various types of engines can be prepared in accordance with the various needs, kinds of vehicles, and the like without substantially involving cost increase.
The separation of the engine body from the transmission section can prevent the heat from the engine from being directly transferred to the transmission device. Therefore, a V-belt and the like members can be used for a long time and the reliability can thus be improved.
Furthermore, the crank case and the transmission case are both formed to provide L-shapes in plan views so as to be opposed to each other and overlapped at longitudinal portions of the L-shaped sections in the width direction of the motorcycle body. Therefore, the space can be effectively utilized.
Still furthermore, the formation of the space can increase a heat insulation function, and hence, the temperature increasing in the transmission case can be prevented. Moreover, the exhaust port of the transmission case is formed so as to be opened to this space, so that air-flow is caused in the space, thus increasing the function for preventing the temperature increasing in the transmission case, thus being available.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.